Sand blasting machine



Sept. 6, 1932. 1 w, V s 1,875,994

SAND BLASTING MACHINE Filed Oct. 50, 1925 2 Sheets-Sheet 1 ATTORNEY.

l. W. DAVIS SAND BLASTING MACHIN E Sept. 6, 1932.

Filed Oct. 30, 1925 2 Sheets-Sheet 2 2 o b 7 7 m a q 6 w 6 W a n 9 a l c 2 2 INVENTOR.

ATTORNEY.

Patented Sept. 6, 1932 IRVIN W. DAVIS, 01 SOUTH MILWAUKEE, WISCONSIN SAND BLASTING MACHINE Application filed OctoberSO, 1925. Serial No. 65,718.

This invention relates to machines for the purpose of performing the operation of sandblasting, and is directed more particularly to producing a machine whereby such operations 5 may be erformed automatically and permit ting adJustment to suit a variety of kinds, sizes, and shapes of work pieces. It will be understood that the term sand-blasting as here used is directed toward an operation of cleaning or abrading the surfaces of work pieces by the means of an abrasive in the form of small loose particles carried by an air stream directed against the surface of the work to be cleaned or abraded. The abrasive used is usually sand and is referred to herein as sand, but the term sand as here used is meant to imply sand or any abrasive substi-,

tute therefor.

' A main purpose is to provide a machine in which the operations of loading the work, sand-blasting it and unloading are performed in a continuous cycle and with a minimum of operative attention. a

Another purpose is to provide mechanism for sand-blasting in which each piece will be subjected to precisely similar treatment without special attention from the operator and in which the various surfaces of a given work piece either may be treated all substantially alike, or certain predetermined portions of such surfaces may be treated less or more than others in accordance with the adjustments or setting of operative portions of the machine, and associated mechanism. An-

other purpose is to provide a mechanism in which the work is traversed in and out of a sand blast chamber,and when travelling in and out a substantially closed chamber to confine the sand and dust incidental to the process is continuously maintained. Another object is to provide sand blast mechanism in which the work is so supported and so operated upon that frail or brittle work pieces, or work pieces combining heavyportions and frail portions may be operated upon without the danger of damage by distortion or break age, and without the necessity of special attention from the operator. v Another purpose is to provide power movement of the work, not only for movement in and out of the chamber above referred to but likewise other movement to present different work surfaces successively to be operated upon, and to provide movementof certain of the sand blast nozzles in synchronism or accordance with the movement of the work pieces whereby improved results may be accomplished and in less operating time.

Another object 'is to successively operate upon a series of work pieces by a series of sand blast nozzles, part of all of which are power movable and part or all of which are adjustable to suit a variety of work pieces or to change the effect on a given size or type of n work piece, and by the means of mechanism permitting ready accessibility to the nozzles for this adjustment, even when the mechanism is in operation.

Another object relates to improved means for confining within a prescribed work chamber the sand and dust incidental to the operation of a sandblasting machine, thereby improving the production time and quality of the product and promotingflthe con venience, safety, and health of the operator.

Another object is generally to simp i improve the design, construction, and operation of sand blast machines.

In the accompanying drawings is shown a sand blast machine incorporating my invention in one of its preferred embodiments, and like reference characters denote like parts in each of the several views of which blast nozzles. Fig. 6 is a partial enlarged section along line 66 of Fig. 2. A rotatably supported vertical central shaft 1 is actuated from any convenient source of p0wer by the means of a belt or other driving means applied to a pulley 2-fixed on a rotatably supported horizontal shaft 3, power bey and ing transmitted from shaft 3 to shaft 1 by the means of the intermeshing bevel gears 4 and 5. Fixed to revolve with and at the upper end of shaft 1 are a series of projecting work supporting arms 6 suitably braced by members 7 and spaced apart at their outer ends. Attached to the outer ends of the arms 6 are bearings 8, rotatably supporting the vertical shafts 9 at the lower ends of which are fixed removable work holders suited to the work to be operated upon. In the present instance the work pieces 10 have a flange 11, and the work may be supported to be readily inserted and removed by the means of hook members 12, pivoted in a member 13 removably fixed to revolve with shaft 9.

As the shaft 1 is rotated the work pieces 10 supported from the arms 6 move bodily one after another in the direction'of the arrow shown in Fig. 1, and are passed into the one end and out of the other end of a com paratively long and narrow chamber. This chamber is designated generally by the letter a and is formed by a substantially closed inner wall 14"and outer wall 15, a lower closure being formed by a perforated plate 16 connecting the walls 14 and 15 together, an upper closure being formed by two plates 17 and 18 suitably attached to the respective side walls and providing a space orslot 19 through which the bearings 8, together with shafts 9, may pass as they are moved by the ,rotation of shaft 1.

, The slot 19 would permit practically unrestricted egress for the dust set up by the sand blast process if means were not provided to prevent such a condition, and to prevent this effect and for other reasons a chamber generally designated by the letter 6 is provided to extend substantially the entire length above the main chambl a, and

#has likewise an upper slot 20 for the-passage of the bearings 8 and shafts 9, similar to the slot 19.

A plate member or strip or structural portion 21 connects together the various bearings 8, and thus ats as a spacing. member for the outer ends of the arms 6, and being disposed directly above the slot 20 and close to the plates which form the upper wall of the chamber 6, and being of greater width than the slot 20, effectually closes the opening or slot 20 throughout its entire length while still "permitting the shafts 9 totra'vel in the slot.

The ends of the chamber I) must provide 'open slots for the passage of the bearings 8,

but such slots are relatively small in width,

being only slightly larger than the outside diameter of the bearings, and therefore comparatively simple. means may be used for closing the slots when not,filled \by the bearings. One simplemeth6d of acEomplishing I such a closure is shown in Fig. 6, a strip of flexible material 8a being fastened to be struck by the bearings 8, whereupon it will parted by. the shaft 1, in order to be more readily removed and replaced.

For the purpose of imparting movement to the shafts 9 and therefore to the work pieces 10 supported therefrom when the work pieces are inside chamber a, the upper end of each shaft 9 is provided with a friction pulley 22 fixed with the shaft and adapted for engagement with a friction bar or rack 23 whenever the pulley reaches a certain point in its travel. The bar or rack 23 is positioned to contact with the "pulleys 22 before the particular work piece reaches the first sand blast nozzle, and .is of such extent as to continue the contact and hence the rotations of the work piece until after the particular work piece has passed the last sand blast nozzle, and when the pulleyv is in contact with the bar or rack and the shaft 1 is in motion to bodily move the pulleyl, such frictional contact will cause the u ey and therefore the shaft 9 and work piece 10 to revolve on the axis of the shaft 9.

In the present machine is shown a series of four sand blastnozzles respectively denoted b the general numerals 24, 25, 26 and 27. 'Rhese nozzles all provide for ejecting a stream of sand at high velocity by the means of a jet of air under considerable pressure directed into the sand as it passes through the nozzle. Nozzle devices for such a purpose are well known, although it is contemplated that the nozzles used in this machine shall be of an improved type shown and later particularly described. Each of the nozzles is so constructed that the nozzle portion proper, from which the blast or stream of sand is ejected may be adjusted in relation to the main or supporting portion, which in turn may likewise be adjusted in relation to the other portions of the machine. In the nozzle 24, the construction of which is typical ofthe other nozzles, the portion 28 is pivoted on the portion 29 to move about an axis 29a and may be retained thereon in various ositions of adjustment by a bolt 30. Simi arly the nozzle '25 has the portion 31'pivoted with the portion 32 to move about an axis 32a. The nozzle 26 has theportion 33 pivoted with the portion 34. The nozzle 27 has the portion 35-1,.

and arranged to be automatically odily moved as each of the work supports and the work supported thereby passes the nozzle, by means which are similar for the two nozzles and will now be described in detail for the nozzle 25.

The nozzle 25 projects into the main chamber a, through an opening 37 in the wall 14, and over the opening is a chamber 38 having walls providing a complete closure when in place, but some of which, as for instance the wall 39, are removable for the purpose of adjusting theportions 31. The nozzle 25 is fixed with a downwardly projecting. shaft or rod 40, there being a suitable bearing provided in the lower walls of the chamber 38 for the shaft 40.

Fixed with the nozzle 25 is an upwardly projecting rod 41, the"'rods 41 and 40 having the same axis. A bearing is provided for the rod 41 in a member 410 which is suitably supported from one of the stationary walls. The entire nozzle 25 is thus pivoted from the rods 40 and 41 and may swing freely. An enlarged portion 416 of the nozzle 25 fits closely but rotatably in an opening of the upper wall of the chamber 38, the opening and the portion 4:16 being of circular form and concentric with the common axis of the rods 40 and 41.

The upper end of the shaft or rod 41 has an arm or extension 416 normally retained in a position 41a, shown in dotted outline in Fig. 1, by the means of a spring 42. When in such position the end ofrod 41 will be successively contacted by the bearings 8 during their travel and will be moved by them against the tension of spring 42 until the continued movement of the bearing carries it outside the length of the rod 41?) when the rod will return abruptly to the position 41a, being pulled back by spring 42 and will thus stand ready to be contacted and moved by thenext following bearing, the arrangement being such that this occurs almost immediately.

Such movement of the arm or extension 416 sets up an oscillation or movement of the nozzle 25 fixed with Fad 41% causing, the nozzle to be moved over an arc of movement which may, by suitable adjustment and proportioning of the various parts, cause the sand issuing therefrom to be directed over the upper surface of the particular work piece which is supported from the particular shaft 9 which is carried by the particular bearing 8 which has contacted rod 416 and thereby caused the movement of the nozzle. It will be seen that the relationship is such that the sand blast follows the bodily movement of a work piece to impinge thereon during a considerable linear travel of the work piece and is then abruptly returned to the starting point to at once start to operate on the next work piece, which has meanwhile been moved into position. Such an arrangement results in an extremely high eificiency.

The rotary movement of the work piece about the axis of shaft 9 and the bodily work movement combined with the sweeping movement of the nozzle 25 caused as described by the successive bearings contacting the rod 41?), may be combined with a suitable adjustment of the nozzle 25 to cause the sand jet issuing therefrom to be directed against every portion of .the upper surface of the work piece, as the work progresses past the nozzle, and the arrangement whereby the sand blast follows along with the work piece allows a relatively very large actual blast period for each work piece whereby the speed of bodily and rotational movement of the work piece may be relatively high, resulting in relatively high production from the machine. Air under pressure is supplied to the nozzle 25 through a duct or channel 44 and sand is supplied through a channel or duct 45. Referring to Figs. 4 and 5 the air channel 44 is car ried throughout the member 32 and communicates with a channel or chamber 46 in the pivoted or adjustable portion 31a. At the point where the air channels 44 and 46 communicate one or the other is elongated so that communication will continue between the channels despite the relative movement of the parts.-

The sand channel communicates with a channel 47 in the pivoted or adjustable nozzle portion 3111 but no slotting is required since they communicate on the axes of adjustment. The sand nozzle 31 is directed out of thechamber 47 of the main portion 31a. In Fig. 5 the nozzle 31 is shown as a separate and removable piece, held in the part 31a by the screw 48, although it is to be understood that the construction may be in one piece with the main pivoted portion and still be effective in operation. Air from the chamber 46 is directed along the bore of the nozzle 31 by the means of an air nozzle 49 removably'fixed in the part 31a by the means of a threaded shank portion and having a bore 50 for communicating with chamber 46 and for directing the flow of the air along the bore of nozzle 31 the bores ofnozzles 31 and 49 being aligned Access to the air nozzle 49, for the purpose of removal and replacement or for other purposes maybe had by the means of a removable threaded plug 51. A slot or other suit able meanstnot shown) may be provided for unscrewing nozzle 49.

The sand nozzle 31 is made removable for replacement because the sand, beihg given a high velocity by the action of the air jet wears away the nozzles, and to prevent as 'much as may be possible the moving sand from striking the side walls of the interior of the sand chamber in the part 31a the nozzle 31- is proyided with an apron or extension 316 projectlng into the chamber. At this point the sand is moving rapidly and must be deflected to pass out through the nozzle 31 and the apron 31?) substantially prevents cutting of the supply of sand as they are rotatedpast the.

spout. The channel 45 is enlarged atits upper part and is carried up close to the lower face of the arms 6 and directly underneath the spout 53. It is provided at its extreme upper portion with flaring or extended wall portions whereby it will catch all of the sand dropped from the spout 53, the flared portions 54 being sufficient to permit of the previously described swinging of the nozzle while still maintaining a sand receiving communication with the spout in any of the nozzle positions.

The nozzle 24 is similarly supported from and pivoted on the rods 55 and 56 and located in a similar chamber 59 having a plate 60 removable for nozzle adjustment. The rod 56 though only partially shown in Fig. 4 extends to "the, top of the structure and has 2. arm or extension 560 which will be contacted by thev various bearings 8 during the passage of the work piece through the chamber a in"- a manner and with an effect similar to the rod 415 previously described in detail. Sand is supplied to the channel 57 and air is supplied to the channel 58 all in a manner and by means similar to the means previously described and used for the same purpose for the nozzle 25, which will be readily understood, but which, having been described for the similar condition existing for nozzle 25, is not again described. The construction of the adjustable nozzle portion-ofthe nozzle 24 is likewise the same as shown for the nozzle 25, and it will be apparent that the nozzle 24 being directed to deliver its sand blast in an upward stream may be so'proportioned, positioned and adjusted that the rotary and bodily movement of the work combined with the, sweeping movement of the nozzle 24 may cause the sand jet issuing from nozzle 24 to be directed against every portion ofthe lower surface of the work during some part of the bodily work travel and with relatively high efliciency'and production, all-in a-manner as previously explained for nozzle 25.

' The nozzles 26 and 27 might have been provided with power movement similar to the movement described forthe nozzles 24' and 25, and it is contemplated that when necessity arises this will be done, but ordinarily it is suflicient to provide merely suitable adjustment of these nozzles. Each of the nozzles 26 and 27 is therefore constructed for swivelling the nozzle portion proper, in a manner similar to the construction illustrated and described for nozzle 25; and are respectively adjustably supported in the chambers 61 and 62 having covers 63 and 64 removable for nozzle adjustment. The shanks of the nozzles 26 and 27 are provided with extension plate portions 65, which are bolted to plate members 66 by the means of bolts a for which slots are provided to permit the nozzles 26;

and 27 to have a considerable pivoted movement relative to the plates 66. Plates 66 are adjustably fastened to the upper wall of the respective chambers by the means of bolts 7 66a, for which slots 66?) are provided to give to the passage 70 from a spout 72, the upper end-s of the passages being flared out or en-' larged to form a funnel shaped portion which will maintain a sand-receiving relation with the respective spouts despite the movement of adjustment of the nozzles. Sand is elevated and supplied to the spouts 71 and 72- by any ot the well kntiwn means suitable for the purpose. i

The nozzles 26 and 27 are stationary after being suitably adjusted but their adjustment in combination with the rotation and bodily movement of the work past the nozzles permits them each to be directed over considerable areas of the work surface and to supple ment the action of the nozzles 24 and 25 on such portions of the work piece as may be required.

The various chambers38, 59, 61, 62 withthe respective removable covers, permit inspection of the work, as it progresses through the machine, and adjustment of the various nozzles while the machine is in operation, these chambers forming in reality portions of the main chamber but practically sheltered from the sand blast of the various nozzles.

Means are provided for maintaing substantially closed ends for the chamber a while still permitting free entry and egress of the work as it travels in and out. At each of the chamber ends a series of swinging doors are provided, at least one pair of which will always be closed, although other pairs may be open to permit passage of the work. In

this instance three pairs of swinging doors are provided at each end'of the chamber. On the end where the work enters are the doors 73, 74, 75, 73a, 74a, 7 5a, arranged in pairs and pivoted suitably on pins 7 5b to swing to an open or to a closed position, but normally restrained in a closed position similar to that shown for the pair 75, 7 5a, by the means of suitable springs as for instance the springs 79 and 80 shown for the doors 75 and 7 5a, or by other suitable means such as weights, the

effect being that the several pairs of doors as for instance the pins or stops 81 and 82 for the doors 7 5 and 7 5a, shown in Fig. 1, against which stops the doors are pulled by the springs 79 and 80.

The moving work piece itself might supply the necessary force acting directly against the doors, but it is considered preferable to provide special means, and for this "purpose striker members 76 are fixed with each of the bearings 8 and are of a suitable size, to contact with the doors before the work piece supported therefrom will strike. The action of these striker pieces is clearly-shown in Fig. 1 where some of them are shown in' con tact with the certain'pairs of doors in the act of forcing the doors open. The several pairs of doors are so spaced in relation to the spacing of the work supporting arms and the contemplated greatest dimensions of the work pieces that, as illustrated in Fig. 1, one pair of doors will be closed completely at all times, although the closed pair will be first one and then another of the several pairs as the work progresses in its bodily movement.

It will be noted that the spacing of the V door pairs necessary to accomplish this result may vary considerably, but preferably should be materially diflerent than the spacing of the work pieces.

A similar set of pairs of doors is provided for the other end of the chamber a, consisting of the doors 76b, 77, 78 and 76a, 77a, 78a. These doors form pairs swinging outwardly from the chamber, but normally restrained in a closed position as illustrated for the pair 77 and 77a.' Suitable springs or weights not shown are provided to returh the doors to a closed position" and thestriker members act in a similar manner upon this set as upon the set at the entrance of the chamber, to open the doors against the resistance set up by the closing means.

It will be noted that although one set of doors swings inwardly toward the chamber a and the other swings outwardly, both sets of doors preferably swing in the direction of the bodily movement of the work into and out of the chamber.

Sand ejected from the various nozzles after striking thework pieces falls by gravity to the floor of the chamber which is formed by the perforated plate 16 previously mentioned. Beneath this plate is a storage chamber 0 formed in this instance by the downward extension of the side walls 14 and 15, and the sand passes into this chamber through the perforations shown in plate 16. Various openings are provided into this storage chamber one of which is shown at 83,

Fig. 2, and suitable removable covers as for instance the hinged cover 84 provide closures for the openings but adaptedto be opened for the removal of the accumulated sand.

The various nozzles are constantly eject-x ing considerable quantities of. air into the chamber a, which unless prevented would set up considerable pressure in the several chambers a, b, and c, and would not only seriously interfere with the action of the various jets or nozzles because of a reduction in the efiective pressure of the air jets, but would also cause an outward flow of dust ladened air from all theunavoidable although relatively minute openings from the various chambers to the outer air:

To avoid-such results air is sucked out or exhausted from the several chambers,'preferably at a somewhat greater rate than it is supplied by the several nozzles or jets conibined, whereby a partial vacuum is formed in each of the several chambers a, b, 0 and an inward flow of air is maintained through the various minute openings, and whereby all of the dust ladened air of the interior of the several chambersfis withdrawn through the exhaust system and may be transferred to some unobjectionable location or purified by any suitable one of several well known methods. I

It is preferable that the exhaust means should be connected at an upper level of the chambers and that it should not communicate with the main chamber a, since less of the comparatively heavy sand will then be drawn along with exhausted air stream.

haust systems is attached toor communicates with the pipe 85 for the purpose described, although for the sake of simplicity such means are not shown in the drawings.

A general summary of the action of the device and mechanism herein shown is ,as follows. 1

When the machine is in operation the shaft 1 and the various work holders 12 are continuously moving, passing the .work holders into and out of the substantially closed chamber a. An operator suitably stationed attaches fresh work pieces to the work independently operable to holders before'they are moved into the chamber and removes the finished work pieces after they have passed through the chamber.

During passage through the chamber, the

work is given another predetermined movement, for instance a rotative movement, in addition to its bodily movement, and while being so moved is subjected to the action of a sand jet or blast or a plurality of such jets, one or more of which. may be adj ustably fixed and yet sweep over a predetermined large area of the work piece because of the variety of Work movements, and one or more of which may be adjustable and also power movable in a predetermined path or cycle of movement, bearing a certain effective relationship to the cycle of work movement. The'power movement of work nozzles is preferably such that the blast stream follows the bodily movement of the work piece fora predetermined interval and is then abruptly returned to the starting point to impinge on the next work piece, which has meanwhile moved into range of the blast whereby the blast efiiciency and production of work pieces .is greatly increased. The various movements being predetermined, uniform results may be obtained on successive work pieces without attention from the operator,

' or b an unskilled operator, and the various jets eing adjustable for individual direction and against any desired portion of the work pieces a great variety of results may be obtained with certainty to suit the individual characteristics or form of difierent work pieces. Many other heretofore unknown advantages of operation will also be apparent to those skilled in this art.

It will be understood that my invention, a preferred embodiment of which is shown in the accompanying drawings and described above, is susceptible of a great variety of modifications of structure without departing from the spirit and scope of the invention as defined in the claims herewith.

I claim:

1. In a sand-blast machine, thecombination of a work support movable in a predetermined path, a sand blast chamber substantially inclosing a portion of said path but having an opening for entry of said support, a plurality of movable closures each substantially closesaid opening and spaced apart along said path, mechanism for the movement ofsaid support in said path, and means establishing a motion transmitting connection from said mechanism to one of said closures at intervals approximately corresponding to the movement of said support past the particular closure to be moved.

2. In a sand-blast machine having a work support movable in a predetermined path and transmission mechanism for the movement thereof, the ,combinationof 'asand-blast chamber substantially inclosing a ortion of said path but having a plurality o? openings respectively for entry and exit of Work pieces, a plurality of closures for each of said openings, each independently operable in one direction to substantially close its respective opening and in the other direction to open the closure to permitpassage of the motion transmitting connection with each of said nozzles including a plurality of contact members spaced in accordance with the spacing of said work holders, and a plurality of parts respectively fixed with the respective nozzles for contact by' said members.

4. In a sand-blast machine, the combination of a work holder movable along a predetermined path, a sand blast chamber substantially inclosing a portion of said path but having an opening for Work entry, a plurality of movable closures each independently operable to substanially close said opening, a sand blast nozzle movable within said chamber, and powers means for the movement of said support, each of said closures and said nozzle in a predetermined cycle.

5. In a sand-blast machine, the combination of a plurality of work holders spaced apart and guided for movement one after another along a predetermined path, a chamber substantially inclosing a portion of said path but having an opening for work entry, closing means for said opening including a plurality of doors spaced apart along said path, a sand blast nozzle supported for movement within said chamber, power operated mechanism for the movement of said work holders and other power operated mechanism for the movement of each of said doors and of said nozzle, the last named mechanism being operative upon the respective parts in cycles repeated at intervals corresponding to the movement of a work holder past the part. j

6. In a sand-blast machine, the combination of a plurality of rotatable work holders spaced apart and guided for movement one after another along a predetermined path, a sand blast chamber substantially inclosing a portion of said path, but providing an open-- mg, power operated means for the rotation of said work holders during the passage through a part of the path portion enclosed by said correspond with the movement of a work holder past the nozzle, closing means for said opening including a plurality of devices spaced apart and each movable to a first position providing free passage for a work hold-- er and to a second position eflective to substantially close sa1d opening, and means for operating one of said devices from one of said positions to the other at intervals timed to correspond to the movement of the individual work holders past the device.

7. In a'sand-blast machine, the combination of a series of spaced work holders movable through a predetermined path, a sand blast chamber substantially inclosing a portion of said path, a bodily movable sand blast nozzle within said chamber including a plurality of partsadjustable for altering the blast direction mechanism .for the movement of said work holders successively past said nozzle and mechanism for bodily movement of said nozzle at intervals corresponding to the work holder movement whereby to sweep the sand blast over difierent work pieces in succession, said chamber having an'opening adjacent said nozzle whereby the effect of the nozzle may be observed during the operation on each work piece and the nozzle parts may be adjusted for be'stresults on the different work pieces.

8. In a sand-blast machine, the combination of a central shaft member journaled for rotative movement, a plurality of work support members supported from said shaft member for movement therewith and at equal distance from the axis of said shaft member, work holders fixed to project in the same direction from said work support members, a sand blast chamber adapted for movement therethrough of said work holders as said member is rotated and provided with a wall having a slot for passage of said work support members, and means for substantially closing said slot to prevent passage of air therethrough and comprising aring-like member fixed for rotation with said 'central shaft.

9. In a sand bIa'st machine the combination of a main work chamber provided with a slot,

an auxiliary exhaust chamber adjacent thereto and havinga slot, a series of movable work supports supported, for movement through said main chamber, from members adapted for movement through both of said slots and a closure for exhaust chamber movable with said work holdeis and positioned adjacent one of said slots. I

10. In a sand blast machine, the combination of a work holder, a movable sand blast nozzle, said work holder being bodily movable past said nozzle, means for the simultaneous movement of said work holder and nozv vidual Work pieces zle, and means restraining said nozzle for movement such that the blast therefrom follows the movement of said work holder over a portion of its path.

11. In a sand blast machine, the combination of a series of work holders bodily movable one after another along a predetermined path, a sand blast nozzle movable adjacent Q said path, transmission mechanism for the simultaneous movement of said work holders and nozzle, and means restraining said nozzle for movement such that the blast therefrom moves over a portion of said path, said transmission mechanism being operative to move said nozzle in a cycle such that a blast therefrom follows a work holder through said path.

portion at a rate approximating the rate of work holder movement and returns abruptly -to a starting position.

12. In a sand blast machine, the combination of a rotatably movable work holder, a -movable sand blast nozzle, said work holder being bodily movable to pass said nozzle transmission mechanism for simultaneously affecting all said movements, and means restraining said nozzle for movement such that the blast therefrom follows the bodily move ment of said work holder over a portion of its ath. p 13. In a sand-blast machine, the combination of a-movable sand blast nozzle, a series of work supports equi-dista'ntly spaced and supported for rotation and for continuous bodily movement one after another past said nozzle, and transmission and controlmechanism including means for said bodily movement of said work supports, means for said rotation of said work supports, means for movement of said nozzle, and means establishing a predetermined timed relationship between each of said movements such that work pieces in the different work holders receive an equal duration of blast from said nozzle, the direction of said nozzle movement relative to the direction of said bodily work support movement being such that said blast follows said bodily movement during a portion of the movement'of said nozzle whereby to prolong the efleplt of said blast on indield in said supports. 14. In a sand-blast machine, the combination of a series of work supports equi-distantly spaced and supported for rotative movement and continuously bodily movable along a predetermined path, a sand-blast nozzle supported .for movement adjacent said ,path, mechanism for said bodily support means guiding said cyclic movement of said of nozzle movement to take place during an I,

nozzle for the blast therefrom to follow the direction of bodily support movement during a substantial portion of said cyclic movement.)

15. In a sand-blast machine, the combination of a series of Work supports equally spaced apart and continuously bodily movable in a predetermined path, .a sand-blast chamber substantially inclosing a portion of said path, a movable sand-blast nozzle within said chamber adjacent said path, transmission mechanism for the movement of said supports and for cyclic movement of said nozzle, said transmission mechanism including means for the relative timing of the movements of said nozzle and supports for a cycle interval corresponding to the period required for a work support to move a distance corresponding to the spacing of said work supports, and to take place each time a support passes said nozzle, and means guiding said cyclic movement of said nozzle for the blast therefrom to follow the direction of said bodnozzles means for timing the nozzle cycle to take place durin an interval corresponding to the time requiredfor a work support to move a distance correspondin to the work support spacing, and to take p ace'each time a support passes the nozzle, and means guiding the cyclic movement of one of said nozzles to follow the direction of work support movement during a portion of the cycle of nozzle movement whereby to prolong the action of the blast.

In witness whereof I afiix my signature.

IRVIN W. DAVIS.

ily support movement during a portion of each cycle of nozzle movement.

16. In a sand-blast machine, the combination of a series of work supports equi-dlstantly spaced and continuously bodily movable one after another in a predetermined circular path, a sand blast chamber substantially inclosing a portion of said path, a movable sand blast nozzle within said chamber and adjacent said path, and motion transmitting mechanism for saidbodily, movement and for cyclic movement of said nozzle, said mechanism including means for the relative timing ofsthe nozzle and supports for a cycle of nozzle movement to take place during an interval corresponding to the period required for a work support to move a distance corresponding to the spacing of said supports and each time a support passes said nozzle, and means guiding said movement of said nozzle to prolong the action of the blast therefrom on Work pieces associated with said work supports.

17 In a sand blast machine the combination of a series of Work supports substantially equally spaced apart and-continuously movable one after another along a predetermined path, a plurality of sand blast nozzles supported for movement adjacent said path and spaced apart in the direction of work support movement, and transmission mechanism for said movement of. said supports and cyclic movement of each of said nozzles, said mechanism including means for 1 a relative timing of the cycles of the diflerent nozzles to correspond with the interval re- 7 quired for the movement 0f one of said work supports from the one to the other nozzle,

said mechanism including for each of said 

